Method of attaching an element to a panel

Abstract

A method of attaching a self-attaching element, including a self-piercing element, to a panel in a die member. The self-attaching element includes a tubular barrel portion having a free open end and may include a piercing surface at the free end of the barrel portion. The die member includes an annular concave die cavity which surrounds a center die post. The method includes coating at least the tubular barrel portion with a fluorocarbon coating, such as polymerized tetrafluoroethylene, prior to the installation of the fastening element to the panel. The tubular barrel portion is then driven through an opening formed in the panel generally coaxially aligned with the die member center post. The opening may be preformed or more preferably pierced by the piercing surface of the barrel portion. The coated internal surface of the tubular barrel portion is then driven against the external surface of the die post, and then against the bottom surface of the concave die cavity, forming a channel-shaped end portion which receives the edge of the panel, forming a mechanical interlock. The friction-resistant fluorocarbon coating on the barrel portion significantly improves the panel installation, including the integrity of the joint, torque resistance and sealing.

I claim: 
     
       1. A method of permanently attaching a self-riveting element to a panel in a die member, said self-riveting element having an integral tubular barrel portion, said tubular barrel portion having internal and external surfaces and a free open end, said die member having an annular concave die cavity surrounding a center die post, said center die post having an external surface blending into a bottom surface of said concave annular die cavity and said die post having an external diameter generally equal to an internal diameter of said tubular barrel portion internal surface, said method comprising the following steps: (a) coating at least said tubular barrel portion internal surface with a solid fluorocarbon lubricating coating;   (b) driving said tubular barrel portion free end through an opening formed in said panel, said opening generally coaxially aligned with said die member center post; and   (c) driving said coated tubular barrel portion internal surface against said die post external surface and then against said concave die cavity bottom surface, thereby permanently expanding said barrel portion free end and forming a channelshaped end portion, said channel-shaped end portion entrapping a panel portion adjacent said panel opening and forming a mechanical interlock between said tubular barrel portion and said panel.   
     
     
       2. The method of permanently attaching a self-riveting element to a panel as defined in claim 1, characterized in that self-attaching element includes a body portion integral with said barrel portion, said body portion having a driving surface extending generally transversely to said tubular barrel portion, said method including coating said internal and external surfaces of said tubular barrel portion with said fluorocarbon coating, and driving said body portion driving surface against said panel portion, thereby driving said panel portion against said tubular barrel portion external surface into said tubular barrel portion channel-shaped end portion, entrapping said panel portion. 
     
     
       3. The method of permanently attaching a self-riveting element to a panel as defined in claim 1, characterized in that said barrel portion free end includes a piercing surface, said method including coating at least said external and internal surfaces of said tubular barrel portion with said fluorocarbon coating, driving said barrel portion piercing surface against said panel to pierce said panel opening, and driving said tubular barrel portion through said pierced opening forming said channelshaped end portion and forming said mechanical interlock. 
     
     
       4. The method of permanently attaching a self-riveting element to a panel as defined in claim 1, wherein said self-riveting element includes a body portion integral with said tubular barrel portion, said body portion including means for attaching said element to a structural member and said method including coating the exterior surfaces of said self-riveting element and body portion with said fluorocarbon coating. 
     
     
       5. A method of permanently attaching a self-riveting element to a panel in a die member, said self-riveting element having a body portion and an integral tubular barrel portion, said body portion having an external diameter greater than an external diameter of said tubular barrel portion defining a bearing surface extending generally transverse to said tubular barrel portion, said barrel portion havinginternal and external surfaces and a free open end, said die member having an annular concave die cavity surrounding a center die post, said center die post having an arcuate concave exterior surface blending into a concave arcuate bottom surface of said annular die cavity, said center die post exterior surface having a diameter generally equal to an internal diameter of said tubular barrel portion, said method comprising the following steps: (a) coating at least said internal and external surfaces of said tubular barrel portion with a fluorocarbon coating;   (b) driving said tubular barrel portion free end through an opening formed in said panel, said opening generally coaxially aligned with said die member center post; and   (c) driving said coated tubular barrel portion internal surface against said center die post arcuate concave exterior surface permanently expanding said barrel portion free end to conform to said die post arcuate concave exterior surface and then driving said barrel portion internal surface against said die cavity concave arcuate bottom surface, thereby forming a channel-shaped end portion, and simultaneously driving said body portion bearing surface against a panel portion adjacent said panel opening, thereby driving said panel portion against said tubular barrel portion exterior surface into said channel-shaped end portion, entrapping said panel portion.   
     
     
       6. The method of attaching a self-riveting element to a panel as defined in claim 5, characterized in that said panel portion free end includes a piercing surface, said method including coating said self-riveting element body and barrel portions with said fluorocarbon coating, driving said barrel portion piercing surface against said panel to pierce said opening, and driving said tubular barrel portion through said pierced panel opening, forming said channel-shaped end portion and forming said mechanical interlock. 
     
     
       7. A method of attaching a self-piercing and riveting element to a panel in a die member, said self-piercing and riveting element having a tubular barrel portion, said tubular barrel portion having internal and external surfaces and a free end having an opening therethrough and said free end having a piercing surface, said die member having an annular concave die cavity surrounding a center die post, said center die post having an external surface expanding in diameter and blending into a bottom surface of said concave annular die cavity, and said die post having a minor external diameter generally equal to an internal diameter of said tubular barrel portion internal surface, said method comprising the following steps: (a) coating at least said tubular barrel portion internal and external surfaces with a fluorocarbon coating;   (b) supporting said panel on said die member overlying said die cavity;   (c) generally coaxially aligning said tubular barrel portion and said die member die post and driving said piercing surface against said panel to pierce an opening through said panel generally coaxially aligned with said die member center die post;   (d) driving said tubular barrel portion through said pierced panel opening and telescopically receiving said center die post in said open end of said tubular barrel portion, said center die post external surface receiving said barrel portion internal surface and permanently expanding said tubular barrel portion free end; and   (e) continuing to drive said tubular barrel portion into said die cavity, said die cavity bottom surface deforming said tubular barrel portion free end radially outwardly and forming a channel-shaped end portion generally U-shaped in crosssection, said channel-shaped end portion entrapping a panel portion adjacent said pierced panel opening and forming a mechanical interlock between said channel-shaped end portion said panel portion.   
     
     
       8. The method of attaching a self-piercing and riveting element to a panel as defined in claim 7, characterized in that self-piercing and riveting element includes a body portion integral with said tubular barrel portion, said body portion having an external diameter greater than said tubular barrel portion and defining a bearing surface extending generally transverse to said tubular barrel portion, said method including coating said body and barrel portions with said fluorocarbon coating, driving said body portion bearing surface against said panel portion, thereby entrapping said panel portion between said body portion bearing surface and said channel-shaped end portion of said barrel portion.